1. Field of the invention
The present invention relates to a finish composition for a high tenacity synthetic fiber for reinforcing plastic composites, the fiber treated with the composition, and reinforced plastic composites incorporating the treated fiber.
2. Description of Related Art
Synthetic fibers in staple or filamentary form, and fabrics produced therefrom, are known for polymer reinforcement. Typical of the fibrous reinforcements are glass, polyester, polyamide (nylon and aramid) and polyolefin fibers. Conventional matrix resins include thermoplastics, such as nylon and polyolefins, and thermosetting materials, such as epoxy and unsaturated polyester resins. In a composite structure the adhesion between the reinforcing fiber and matrix is a determining factor in the load sharing ability of the composite.
U.S. application Ser. No. 631,978, filed July 18, 1985, discloses a high tenacity reinforcing fiber selected from the group consisting of polyester, aliphatic polyamide and combinations thereof, for reinforcing composites. The reinforcing fiber is treated with a composition comprising an aqueous solution of carboxyl-terminated, oil-free alkyd resin which is the reaction product of at least one aliphatic glycol containing 2 to 12 carbons with a combination of aromatic di- and trifunctional carboxylic acids. Optionally, unsaturated aliphatic acids may be included with the carboxylic acids. These alkyd resins are polymerized below their gel points, that is the degree of esterification is generally maintained below about 90 percent.
Replacement of glass fiber, or a portion of the glass fiber, in a reinforced composite with the synthetic fiber treated as disclosed above has been shown to provide great improvement in notched impact strength of the resulting composite.
The fiber so treated additionally has been found to possess a high degree of fiber bundle integrity. Fiber bundle integrity is the degree to which the individual filaments adhere to each other. The main benefit of a low integrity fiber is that it enables good dispersion of single filaments throughout a resin matrix. This even distribution results in a homogeneous reinforced composite, a direct result of which is an improved cosmetic appearance. However, in operations where high speed cutting, on the order of 500 feet/minute (about 150 m/min) or higher, of the fiber is required, a low integrity fiber tends to fluff or cottonball and jam up the cutter. A high integrity fiber, readily cut a high speed and which does not ball-up within the reinforced composite, is therefore desirable.
However, additional improvement in the finish composition is desirable. It has been found that when the finish composition discussed above is applied to high tenacity synthetic filamentary yarn, and the treated yarn is packaged for customer use, blocking problems may result from the packaging and storage of the treated yarn. By blocking problems it is meant that the tackiness of the finished yarn causes yarn filaments in adjacent yarn bundles to stick together on the package. Upon removing the yarn from the package, filaments from adjacent bundles stick to the yarn being removed, causing production problems for the customer.